1. Field of the Invention
The invention relates generally to the field of wellbore intervention using spoolable rods or tubes. More specifically, the invention relates to methods for sealing leaks in such rods or tubes while the rod or tube is disposed in a wellbore.
2. Background Art
In the extraction of oil and gas from underground reservoirs, it is frequently necessary to insert tool strings into a wellbore drilled through the reservoir to perform various completion and recompletion tasks.
There is known in the art a semi-stiff (stiff being defined in terms of bending moment), spoolable intervention rod having one or more internal fluid conduits and/or electrical and optical conductors. Such rod is used to provide wellbore intervention services under the name ZIPLOG, with is a mark of Ziebel, AS, the assignee of the present invention. A breakage or leak in the conduit in the spoolable rod below the surface (wellhead) can cause wellbore fluids and/or gas to migrate to the Earth's surface where the fluids can cause a safety hazard. The same gas and/or fluid migration may occur through the rod if seals on a guide nose coupled to the lower end of the rod fail to seal, or this guidenose is broken off the rod downhole.
Systems are being currently being developed and introduced for wellbore intervention for deployment of sensors, where the sensors can be incorporated into one of the foregoing semi-stiff, spoolable rod. The rod can be pushed into wellbores that are in operation (i.e. producing or injecting fluid), where the stiffness of the “rod” enables long lateral displacement to be achieved. Henning Hansen et al. describe a methodology for such a spoolable rod system in International Patent Application Publication No. WO 2006/003477 entitled “Intervention rod”. The foregoing described rod is the same as that used to provide the previously stated ZIPLOG services.
Also there are systems known in the art that are based on pushing a spoolable, small diameter tubing associated with the rod into wellbores for purposes such as chemical injection, as for example, for gas well dewatering. See, e.g., U.S. Patent Application Publication No. 2009/0266537 filed by Hansen et al., and which is commonly owned with the present invention.
In case of breakage or leakage downhole (below the Earth's surface) of such a rod or a small diameter tube, gas or wellbore fluids can migrate to surface where they can become a safety hazard. Spoolable rod and small diameter tube systems normally have one or several pressure barriers implemented in the lower end of the rod or tube being inserted into the wellbore, but the challenge is if there is a leakage within these barriers or leakage or breakage in the rod or tube above these barriers.
Typically a pressure seal, as for example in the form of a valve, can be coupled to the upper end of the “rod” or tube, located outside the wellhead as for example on a surface winch unit, but this is in many instances not sufficient barrier to obtain sufficiently safe wellbore operations with contingency built in.